This invention relates to solvent-based (non-aqueous) aerosol paints containing dimethyl ether as solvent or solvent and propellant.
A solvent-based aerosol paint contains both a propellant and a film-forming paint resin formulation. Most commercial solvent-based aerosol paints contain mixtures of low molecular weight hydrocarbons as the propellant; most commonly, a blend of propane and isobutane is used. A paint resin formulation generally contains a paint resin(s), pigments, diluting and coalescing or film-forming solvents, and various additives, such as drying agents, thickeners, surfactants, antiskinning agents, plasticizers, mildewcides, mar-resistant agents, antiflooding agents, etc.
To form a uniform, smooth coating when a solvent-based aerosol paint is applied to a surface and allowed to dry, the paint resin(s) in the paint must be in a single phase with the solvents and propellant during application. The propellant can also function as a solvent in the paint. The other ingredients in the paint resin formulation, i.e., pigments and additives, may be dispersed or suspended in the paint; however, it is important that the paint resin(s) be in solution for satisfactory application of paints to substrates.
The low molecular weight hydrocarbon propellants are quite poor solvents for many paint resins and additional relatively powerful solvents are required in commercial aerosol paints as components of the diluting and coalescing or film-forming solvents in order to solubilize these resins. The solvents commonly used in solvent-based aerosol paints for solubilization of the paint resins are aromatic compounds such as toluene or xylene, various ethylene glycol ethers and methylene chloride. These compounds are good solvents and produce excellent solvent-based aerosol paints.
A problem with the use of these solvents, however, is their potential toxicity to humans when exposure results during normal use or when deliberate abuse occurs (inhalation). In many instances, the ethylene glycol ethers are being replaced in aerosol paints with the safer propylene glycol ether solvents. However, great difficulty has been experienced in finding good substitutes for the aromatic solvents and methylene chloride and special handling, storage and application procedures may be required in the near future when using aerosol paints which contain these solvents.
The introduction of dimethyl ether (DME) as an aerosol propellant has provided the opportunity to formulate attractive, low-toxicity solvent-based (non-aqueous) aerosol paints without requiring the use of toxic aromatic solvents or methylene chloride.